Aave protocol is a "decentralized, open-source, and non-custodial money market protocol".
Depositors earn interest by providing liquidity to lending pools, while borrowers can obtain overcollateralized loans by using the liquidity from these pools.
Similar to other DeFi platforms (e.g., Compound, Fulcrum), deposits are tokenized as aTokens, which accrue interest in real-time. Aave Protocol supports more than 15 different assets, with a large selection of stablecoins.
LEND tokens are used for fee reductions and will also be used for governance rights at the protocol level for future smart-contract updates. LEND tokens are also burnt from the fees collected from the Aave Protocol.
Since January 2020, Aave protocol also offers undercollateralized solutions: flash loans allow developers to borrow instantly and easily without any collateral.